1. Field of the Invention
The present invention relates to a tomosynthesis system for digital X-ray imaging and a method of controlling the system.
2. Description of the Related Art
In general, medical or industrial X-ray imaging devices which see through a patient's body or an object and capture regions of the body or object using the penetrative property of X-rays are being widely used.
Although an analog film method had been used conventionally, a digital method using a semiconductor flat-panel detector, in place of the analog film method, has been widely used recently.
With regard to the migration to the digital method, a digital imaging apparatus capable of simply acquiring two-dimensional (2D) projection images is accompanied by the problem that it is difficult to make diagnoses when lesions are covered by bodily tissues. Therefore, tomosynthesis systems which capture an object at various angles and synthesize tomograms, thereby considerably improving diagnosis performance, have been developed.
Such a tomosynthesis system detects X-ray images at various angles, creates a 3D projection image of, for example, a patient's breast, and displays the created 3D projection image.
However, the tomosynthesis system is configured such that an X-ray source should move and stop repeatedly, rather than continuously moving, in order to capture X-ray images at various angles. That is, the tomosynthesis system employs a step-and-shoot method in which an X-ray source stops at a capture angle and then captures an X-ray image, moves to another capture angle, and then stops at the latter capture angle and then captures another X-ray image.
Even if an X-ray source continuously moves, blur (which makes the contour of an image indistinct) occurs in images formed in a stationary detector due to the movement of the X-ray source during the exposure time of each X-ray capture, thereby deteriorating the quality of the images.
FIG. 1 is an exemplary diagram illustrating the principle of capturing which is performed while the X-ray source of a conventional tomosynthesis system continuously moves.
As shown in FIG. 1, in the case where an X-ray source continuously moves, the X-ray source moves by ΔXS during exposure time Δt, and an X-ray focus also moves as the X-ray source moves. Accordingly, an image formed in the detector also moves by ΔXD as the X-ray source moves, so that blur occurs.
In particular, the blur of images increases proportional to the speed of the X-ray source and the exposure time of X-rays.
Since the X-ray source moves over a predetermined angle while repeatedly moving and stopping as described above, mechanical instability occurs and the scan time may only limitedly be reduced. In particular, when the number of captures is large, the scan time increases because of a large number of times the X-ray source moves and stops, thereby increasing patients' pain and inconvenience.